Sam opened the cover of his book and sat at the table. Dean and Cas were on a walk so he had some time for himself. About 3 chapters in, he felt cold air graze the back of his neck. As an instinct, he grabbed for a gun that was carelessly set on a bookshelf and pointed it in the direction the cold air was coming from. Years of hunting ghosts had taught him this. After a few seconds he still felt the low temperature and noticed the door was left open. Sam shook his head and put the gun down. He heard voiced and realized it was Deans and Cas's. Knowing they were close, he left the door open and took his book to his room.
Dean closed the door behind them once they have stepped in and heard an inhuman screech of terror. Right next to the door was Cas on the floor with a terrified look on his face. "Cas! Whats wrong!?" Asked the worried hunter. Cas just pointed with a shaker finger in the direction of the staircase. "C'mon." Dean put out his hand for Cas to take. They both walked stealthily down the stairs and into the main room. A small figure scurried about 5 feet away from them which made Cas jump and clutch Deans arm. "What is it?!" Cas stressed. Dean relaxed and saw a tail peak out from behind a bookcase. "Its a mouse Cas!" When Cas saw Dean relax so did he. "They're harmless." He laughed.
He felt something brush against his foot and looked down to see the mouse rush to the room behind them and turn into the hallway. Now Dean grabbed for Cas's arm, and Cas was still holding onto his. Dean put a finger to his lips to signal Cas to be quiet. Holding onto each other, they quietly walked to the hallway. The mouse turned sharply turned a corner and was now running toward them. "GO! GO! GO!" Dean ordered and they ran as fast as they could into the kitchen. They were both out of breath by the time they reached their destination. "You get a cup and I'll get a pan." He said. "Why get a cup?" Castiel asked, confused. "To trap the mouse with." Dean answered. "And the pan?" "In case we can't trap it." They both rushed for the items and met up right outside the kitchen.
"Ok, you ready?" Cas nodded and they stepped into the hallway. Dean signaled for Cas to go one way and Dean to go the opposite. Cas walked through the hallway and his breathing was loud and heavy, his eyes wide. He flinched at any sound of movement or if he thought he saw something move from the corner of his eye. "DEEEAAAN!" He yelped when he saw the mouse scramble by his feet. Dean ran to him in just a matter of seconds and saw Cas had trapped it in the cup. They took a moment to catch their breath. Dean took off his green jacket and crouched down next to Cas. "Okay, on the count of three, lift up the cup just slightly. One, two, three!" Cas lifted it up just in time for Dean to slide his jacket underneath the cup. "Now let's put him back outside."
Dean picked one hand on the bottom of the jacket and the other on the top of the cup. They walked outside and let the mouse free. It had scampered off into some bush, it seemed proud. Dean turned to Cas, "We are never leaving the door open again."